Highly positioned laser processing nozzle

ABSTRACT

A double nozzle for a laser processing head includes an inner body portion having an interior surface defining a first bore, and an exterior surface, the bore aligned with a central longitudinal axis of the body. The double nozzle includes an outer body portion having an interior surface defining a second bore that is substantially aligned to the longitudinal axis. The outer body portion is matingly engaged with a region of the exterior surface of the inner body portion. The region between the exterior surface of the inner body portion and the interior surface of the outer body portion defines at least six coaxial fluid flow paths through an interior annular flow volume of the double nozzle. Each fluid flow path is defined at least in part by a corresponding feature formed in at least one of the inner body portion or the outer body portion.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/339,077, which was filed on Oct. 31, 2016 and entitled“Highly Positioned Laser Processing Nozzle,” which claims the benefit ofU.S. Provisional Patent Application No. 62/248,943, which was filed onOct. 30, 2015 and entitled “Highly Positioned Laser Processing Nozzle.”This application also claims the benefit of U.S. Provisional PatentApplication No. 62/360,908, which was filed on Jul. 11, 2016 andentitled “Multiple Flow Grooved Highly Positioned Laser ProcessingNozzle.” The entire contents of these applications are incorporatedherein by reference.

FIELD OF THE INVENTION

The invention relates generally to the field of laser cutting systemsand processes. More specifically, the invention relates to improvedalignment of a laser beam and fluid flow within a double nozzle.

BACKGROUND

Material processing apparatuses, such as laser cutting machines, arewidely used in the cutting, welding, and heat treating of materials. Alaser-cutting machine generally includes a high-power laser, a nozzle, agas stream, an optical system, and a computer numeric control (CNC)system. The laser beam and gas stream pass through an orifice of thenozzle and impinge upon a workpiece. The laser beam heats the workpiece,which, in conjunction with any chemical reaction between the gas andworkpiece material, alters (e.g., liquefies and/or vaporizes) a selectedarea of workpiece, allowing an operator to cut or otherwise modify theworkpiece. The laser optics and CNC are used to position and direct thelaser beam relative to the workpiece during a cutting operation. Lasersare frequently used in material processing applications because laserbeams can be focused to small spot sizes, thereby achieving theintensity and power density desired to process industrial-strengthmaterials, such as metals.

In conventional laser cutting systems, alignment of system components(e.g., nozzles) can be critical to system life and performance. Forexample, alignment of the nozzle bore and/or orifice to the nozzleholder and laser cutting head optics can be critical to properfunctioning of the laser cutting process. In addition, alignment of thelaser beam and the gas jet can be critical to achieving uniform cutquality around all sides of the workpiece. One instance in whichalignment issues manifest is during component replacement andinstallation, during which the nozzle bore(s) and/or orifice(s) must bealigned with a longitudinal axis of the laser head, and thus the laserbeam, so as to avoid non-symmetric gas flow about the beam. The problemis compounded because conventional nozzles must be replaced frequently,and each nozzle replacement can involve a complex installation andverification to prove alignment. In addition, because components mustoften be replaced in the field, significant machine down time andtechnician expertise can be required to ensure proper installation andalignment. Field replacement can also require specialized tools toattain, verify, and maintain proper component alignment.

One type of nozzle, a “double nozzle,” has specific benefits for lasercutting applications but also creates unique issues around alignment ofcomponent parts. Structurally, a double nozzle typically has two pieces(e.g., an inner and an outer nozzle portion) that are press-fitted orthreaded together. A primary function of a double nozzle is to createtwo separate flows of gas within an inner and an outer nozzle portion.One flow of gas is delivered through a central bore and positioned alongthe axis of the laser beam itself, while a second flow of gas surroundsthe central bore and provides a coaxial flow of lower pressure gas. Thecentral flow helps to remove material during the cutting process as thelaser beam heats the material and the process gas ejects the materialfrom the kerf, while the lower pressure coaxial flow provides aprotective flow around the central flow, preventing entrainment of airinto the molten kerf and surrounding the kerf with the correct gaschemistry for the material being processed.

FIG. 1 shows a prior art double nozzle configuration. In thisembodiment, a double nozzle 100 includes an inner body portion 102(e.g., inner nozzle portion or inner nozzle) and an outer body portion104 (e.g., outer nozzle portion or outer nozzle) joined at an interfacesurface 124. The inner body portion 102 has an orifice 112 that permitsthe laser beam to pass through the double nozzle 100. The outer bodyportion 104 has an orifice 114 and an alignment surface 122 for aligningthe double nozzle 100 with a laser machining head (not shown). In thisconfiguration, two separate surface interfaces determine alignment ofthe inner nozzle orifice 112 relative to a longitudinal axis 107 of thelaser machining head and thus the laser beam itself: (1) the alignmentsurface 122 with the laser machining head; and (2) the nozzle interface124 between the inner body portion 102 and the outer body portion 104.

The inner nozzle orifice 112 of inner body portion 102 in FIG. 1 issmaller than the outer nozzle orifice 114 and is located closer to thelaser beam during operation than the outer nozzle orifice 114. Thus,alignment of the inner nozzle orifice 112 can be particularly importantto performance and life of the double nozzle 100. The alignment of theinner nozzle orifice 112 with the longitudinal axis 107 of the lasermachining head, and thus the laser beam via two separate interfaces,depends on the accuracy and precision of four separate surfaces thatcreate each of these two-surface interfaces. Therefore, a high level ofmanufacturing precision is required on these four surfaces, as well asinstallation accuracy and verification to ensure proper life andperformance; misalignment in any of these components can have a dramaticimpact on alignment of the inner nozzle orifice 112 relative tolongitudinal axis 107 of the laser beam. What is needed is a doublenozzle configuration that reduces the number of opportunities formisalignment, thereby improving alignment of the laser beam and thenozzle bore and/or orifice, and simplifies installation and operation.

SUMMARY OF THE INVENTION

In some embodiments, the present invention relates to systems andmethods for aligning a laser beam within a nozzle bore and/or orifice ofa laser cutting system. In particular, certain surfaces betweenconstituent parts of the nozzle are re-designed (e.g., the surfacebetween an inner bore of a double nozzle and a longitudinal axis of thelaser machining head) so that the number of interface surfaces (i.e.,opportunities for misalignment) is minimized. In a new configuration inaccordance with the present invention, alignment of the beam and thenozzle bore, and consequently gas shrouding and alignment, are improved.In addition, manufacturing tolerances on nozzle interfaces are loosened,and operation and installation of the system are simplified.

One advantage of the invention is to provide a more uniform secondaryfluid flow and/or an improved functional alignment with respect tostandard designs (e.g., three-milled flats). Another advantage of theinvention is to provide improved alignment of a double nozzle that isnearly equal to that of a single nozzle. Another advantage of theinvention is to enable a more reliable, repeatable operation (e.g.,whether attended or unattended; hand loaded or auto-loaded; and/or handaligned or machine aligned). Another advantage of the invention is tominimize the chance for assembly errors and mixing of parts (e.g.,particularly if outer and inner nozzles are pre-assembled and fastenedwithin a cartridge). Another advantage of the invention is to provide anon-press fit relationship of the inner and the outer nozzle portions.Another advantage of the invention is increase the alignment alongconical surfaces, which can also improve radial alignment. Anotheradvantage of the invention is to enable centering of a nozzle into achamfer or cone region without using a threaded configuration. Anotheradvantage of the invention is to simplify the assembly process and needfor an extensive interference and/or press fit to hold the inner andouter nozzles together.

In one aspect, the invention features a double nozzle for a laserprocessing head. The double nozzle includes an inner body portion having(i) an interior surface defining a first bore, and (ii) an exteriorsurface, the bore aligned with a central longitudinal axis of the body.The double nozzle also includes an outer body portion having an interiorsurface defining a second bore that is substantially aligned to thelongitudinal axis. The outer body portion is matingly engaged with aregion of the exterior surface of the inner body portion. The regionbetween the exterior surface of the inner body portion and the interiorsurface of the outer body portion defines at least six coaxial fluidflow paths through an interior annular flow volume of the double nozzle.Each fluid flow path is defined at least in part by a correspondingfeature formed in at least one of the inner body portion or the outerbody portion.

In some embodiments, the region includes an interface between theexterior surface of the inner body portion and the interior surface ofthe outer body portion. In some embodiments, the coaxial fluid flowpaths are shaped to increase fluid flow and uniformity of fluid flowthrough the double nozzle. In some embodiments, each of the fluid flowpaths is defined at least partially by a corresponding feature in theexterior surface of the inner body portion. In some embodiments, each ofthe fluid flow paths is defined at least partially by a correspondingfeature in the interior surface of the outer body portion. In someembodiments, each of the fluid flow paths includes a scalloped or curvedsurface. In some embodiments, the interface between the exterior surfaceof the inner body portion and the interior surface of the outer bodyportion is at least partially defined by one or more step features. Insome embodiments, each of the features is configured to assist withseating and alignment of the inner body portion relative to the outerbody portion during assembly of the double nozzle. In some embodiments,the substantial alignment is less than about 0.002 inches.

In another aspect, the invention features a double nozzle for a laserprocessing head. The double nozzle includes an inner body portion havingan interior surface defining a first bore, a first exteriorcircumferential surface disposed toward a distal end of the inner bodyportion, and a second exterior circumferential surface disposed toward aproximal end of the inner body portion. The second exteriorcircumferential surface is shaped to mate and align with the laserprocessing head. The double nozzle also includes an outer body portionhaving an interior surface defining a second bore. The outer bodyportion matingly engages with the first exterior circumferential surfaceof the inner body portion and is isolated from direct alignment contactwith the laser processing head. The inner body portion and the outerbody portion are aligned to define a coaxial fluid flow paththerethrough.

In some embodiments, the second exterior circumferential surface istapered relative to a longitudinal axis of the double nozzle. In someembodiments, the tapered surface is at an angle of about 4.5 degrees toabout 5.5 degrees with respect to the longitudinal axis. In someembodiments, the double nozzle further includes a set of fluid flowpaths formed between the inner body portion and the outer body portion.In some embodiments, the set of fluid flow paths is formed at aninterface between the first exterior circumferential surface of theinner body portion and the outer body portion. In some embodiments, theset of fluid flow paths includes six distinct flow paths. In someembodiments, the second exterior circumferential surface includes aconical interference interface with the interior surface of the outerbody portion, the conical interface including a spacing of about 0.001to 0.003 inches between the surfaces. In some embodiments, the innerbody portion and the outer body portion are crimped using a force ofabout 2000 lbF. In some embodiments, the second bore of the outer bodyportion includes an axial stop for positioning relative to the innerbody portion. In some embodiments, the inner body portion has a conicaldatum feature received by the second bore of the outer body portion. Insome embodiments, the inner body portion and the outer body portion canprovide at least about 25% improvement in alignment. That is, the newdesigns and configurations described herein can provide better alignmentthan conventional systems. In some embodiments, the double nozzle isconfigured to provide a better flow profile than some conventionalsystems. For example, in some cases, the systems and methods herein canyield a flow that is more uniform and allow for a wider range ofadjustment in flow rate than some conventional systems. By way of anexample comparison, a 3-slot nozzle can produce pressures that varybetween 1 psi and 1.33 psi, which can be a peak-peak variation of 28%about the mean. Whereas, in some examples, the inventive nozzlesdescribed herein can also produce pressures that vary between 1.51 psiand 1.57 psi, which can be a peak-peak variation of 4% about the mean.In other words, the inventive multiple flow grooved nozzles describedherein can result in ˜7× reduction in flow non-uniformities compared tosome conventional 3-slot nozzles.

In another aspect, the invention features a method of cutting aworkpiece using a laser cutting system. The method includes providing alaser processing head and a double nozzle. The double nozzle has aninner body portion, an outer body portion, and an axial bore. The innerbody portion has a first exterior surface shaped to complement acontoured alignment surface on the laser processing head and a secondexterior surface shaped to complement an interior circumferential matingsurface of the outer body portion. The outer body portion is secured tothe inner body portion along the circumferential mating surface andisolated from direct alignment contact with the laser processing head.The method further includes installing the double nozzle in the laserprocessing head to align to a longitudinal axis of the laser processinghead. The method further includes flowing a fluid through a primary flowpath and at least one secondary flow path formed in the double nozzle.The method further includes generating a laser beam along thelongitudinal axis of the laser processing head. The method furtherincludes cutting a workpiece with the laser beam as it exits the doublenozzle.

In some embodiments, the second exterior surface is tapered relative toa longitudinal axis of the double nozzle. In some embodiments, the taperis at an angle of about 4.5 degrees to about 5.5 degrees relative to thelongitudinal axis. In some embodiments, the double nozzle furthercomprises a set of fluid flow paths formed between the inner bodyportion and the outer body portion. In some embodiments, the set offluid flow paths is formed at an interface between the first exteriorsurface of the inner body portion and the outer body portion. In someembodiments, the set of fluid flow paths includes six distinct flowpaths. In some embodiments, the second exterior surface is a conicalinterference interface with the interior surface of the outer bodyportion, the conical interface including a spacing of about 0.001 to0.003 inches between the surfaces. In some embodiments, the inner bodyportion and the outer body portion are crimped using a force of about2000 lbF. In some embodiments, the second bore of the outer body portionincludes an axial stop for positioning relative to the inner bodyportion. In some embodiments, the inner body portion has a conical datumfeature received by the second bore of the outer body portion. In someembodiments, the inner body portion and the outer body portion canprovide at least about 25% improvement in alignment. That is, the newdesigns and configurations described herein can provide better alignmentthan conventional systems. In some embodiments, the double nozzle isconfigured to provide a better flow profile than some conventionalsystems. For example, in some cases, the systems and methods herein canyield a flow that is more uniform and allow for a wider range ofadjustment in flow rate than some conventional systems. By way of anexample comparison, a 3-slot nozzle can produce pressures that varybetween 1 psi and 1.33 psi, which can be a peak-peak variation of 28%about the mean. Whereas, in some examples, the inventive nozzlesdescribed herein can also produce pressures that vary between 1.51 psiand 1.57 psi, which can be a peak-peak variation of 4% about the mean.In other words, the inventive multiple flow grooved nozzles describedherein can result in ˜7× reduction in flow non-uniformities compared tosome conventional 3-slot nozzles.

In some embodiments, the contoured surface of the nozzle has an arcuateshape and may be sectioned or may have a tapered alignment surface topromote even seating. In some embodiments, the inner nozzle has all ormany of its “flow-creating” features positioned highly to a taperedseat. In some embodiments, the outer nozzle is highly positioned toinner and fastened to ensure alignment, safe operation at high pressure,seal of gas and conductivity of capacitive circuit. Because slip fits,press fits, and diametrical mating features have inherent variation, inorder to ensure consistent performance, tight tolerances must bemaintained on double nozzles of this design (tolerances that aredifficult to achieve even with high precision CNC lathes).

In some embodiments, an interface surface between the double nozzle andthe laser machine head is formed directly on the inner body portion ofthe double nozzle. In some embodiments, complementary countered surfacesare formed on the machining head and the inner body portion, which cancenter and align the bore with the longitudinal axis of the head. Insome embodiments, the invention features both of these improvements in a“hybrid” design. In such embodiments, the invention can include atapered seat on the inner nozzle component to functionally align theprimary gas flow with the laser beam and head. The nozzle bore and theangled functional datum feature can be machined simultaneously such thatthey are highly positioned and coaxial. In some embodiments, the doublenozzle design is further improved with a tapered or shaped interfacebetween the inner nozzle and the outer nozzle, such that the radialposition errors are minimized through hard contact of the tapered orshaped surfaces. This tapered contact method can improve coaxiality atthe expense of axial alignment, which can be functionally less sensitiveor critical. In some embodiments, the tapered seat on the inner nozzleand the shaped interface between the inner and outer nozzle areseparable concepts, which may be used together or separately to achievethe results and benefits described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing discussion will be understood more readily from thefollowing detailed description of the invention when taken inconjunction with the accompanying drawings.

FIG. 1 is a cross-sectional diagram of a prior art double nozzle for alaser cutting system.

FIG. 2 is a cross-sectional diagram of an improved double nozzle for alaser cutting system, according to an illustrative embodiment of theinvention.

FIG. 3 is a three-dimensional half-sectional view of an improved doublenozzle for a laser cutting system, according to an illustrativeembodiment of the invention.

FIG. 4 is a cross-sectional diagram of an improved double nozzle for alaser cutting system in which the inner body portion is conically seatedwithin the outer body portion, according to an illustrative embodimentof the invention.

FIGS. 4A-4B show perspective views of double nozzles having more thanthree slots, according to illustrative embodiments of the invention.

FIG. 5A shows a three-dimensional measured flow mapping of a standardthree-slot design for a double nozzle.

FIG. 5B shows a three-dimensional measured flow mapping of a six-groovedesign for a double nozzle, according to an illustrative embodiment ofthe invention.

FIG. 6 shows a perspective view of an inner body portion of a doublenozzle, according to an illustrative embodiment of the invention.

FIG. 7 shows a cross-sectional view from the side of the nozzle of onepossible step feature of a double nozzle, according to an illustrativeembodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 2 is a cross-sectional diagram of an improved double nozzle 200 fora laser cutting system, according to an illustrative embodiment of theinvention. The double nozzle 200 includes an inner body portion 202having an interior surface 203 defining an inner nozzle bore 205 and aninner nozzle orifice 212. The inner body portion 202 has a firstexterior circumferential surface 223 disposed toward a distal end 209 ofthe inner body portion 202. The inner body portion 202 has a secondexterior circumferential surface 222 disposed toward a proximal end 221of the inner body portion 202. The double nozzle 200 also includes anouter body portion 204 having an interior surface 225 defining an outernozzle bore 211 and an outer nozzle orifice 214. The second exteriorcircumferential surface 222 is shaped to mate and align (e.g., directly)with the laser processing head (not shown). The outer body portion 204is matingly engaged with the first exterior circumferential surface 223of the inner body portion 202 and is isolated (e.g., substantially) fromdirect alignment contact with the laser processing head. The inner bodyportion 202 and the outer body portion 204 are aligned to define acoaxial fluid flow path 231 therethrough.

Generally, the double nozzle 200 has similar external and internaldimensions to the prior art double nozzle 100 shown and described abovein FIG. 1. However, the double nozzle 200 has fewer interface surfacesbetween the inner nozzle bore 212 of the inner body portion 202 and thelongitudinal axis 207 of the laser beam. Specifically, the double nozzle200 has one interface as a result of forming the second exteriorcircumferential surface 222 (the nozzle machining head interfacesurface) directly on the inner body portion 202. Thus, the reduction ininterface surfaces can be due to a relocation of the interface 224between the inner and outer body portions 202, 204, as compared with theinterface 124 of the prior art. Such a re-configuration reduces thenumber of “direct alignment contact” surfaces, e.g., surfaces thatcontrol alignment of inner nozzle bore 212 relative to longitudinal axis207 (even though, in some configurations, some physical contact may bepresent between the surfaces). In this case, the number of directalignment contact surfaces is two (i.e., the nozzle machining headinterface surface 222 and its complementary surface on the laser head)from the four surfaces shown in the prior art configuration of FIG. 1.Thus, the double nozzle 200 provides a more direct connection betweenthe longitudinal axis 207 and the inner nozzle bore 212, loosensmanufacturing requirements on outer body portion 204, and reducesinstallation complexity and verification procedures. In thisconfiguration, the laser beam and the gas flow can be insulated fromdirect effects of any assembly errors.

In some embodiments, the inner and outer body portions 202, 204 may beaffixed by a variety of methods including friction welding or pressfits. In some embodiments, the nozzle machining head interface surface222 of the double nozzle 200 can include a contoured surface shaped tocomplement a contoured alignment surface on the laser machining head.Thus, when a technician installs the double nozzle 200 in a lasermachining head, the contoured surface of the double nozzle 200 mateswith the contoured alignment surface of the laser machining head,facilitating alignment of the double nozzle 200 with the longitudinalaxis 207. This alignment occurs because as the double nozzle 200 isinstalled in the laser machining head, the contoured mating surfacecontacts the first contoured alignment surface centering the doublenozzle 200, thereby causing the longitudinal axis 207 of the doublenozzle 200 to align with the torch axis and thus the laser beam. As aresult, the double nozzle 200 becomes centered about the laser beam toprovide a concentric uniform annular gas flow about the laser beam tofacilitate torch operation. This radially-centered double nozzle 200avoids the field replacement and alignment problems of the prior art,and/or reduces or eliminates the high precision manufacturingrequirements of multiple parts.

In some embodiments, the contoured surface is an arcuate section and/ora linear taper. Such an arcuate section can have a fixed radius ofcurvature or several radii of curvature. Contoured or tapered alignmentsurfaces can promote even seating and alignment of the double nozzle 200and the inner nozzle bore 212 relative to the longitudinal axis 207. Theangle formed between the taper and the axis of the laser beam can be anyvalue less than 90 degrees, preferably less than about 45 degrees and,more preferably, less than about 20 degrees. Such configurations canhelp to pair contoured mating surfaces with contoured alignment surfacesto centrally dispose the double nozzle 200 along the longitudinal axis207.

FIG. 3 is a three-dimensional half-sectional view of an improved doublenozzle 300 for a laser cutting system, according to an illustrativeembodiment of the invention. The double nozzle 300 includes an innerbody portion 302 having an inner nozzle bore 312 and an outer bodyportion 304 having an outer nozzle bore 314, both of which are orientedalong a longitudinal axis 307 of the laser beam. The double nozzle 300has a similar configuration to the double nozzle 200 shown and describedabove in FIG. 2, with several notable differences. For example, in thisconfiguration, the interface 324 between the inner body portion 302 andthe outer body portion 304 is tapered in a “conical seating” arrangementwith respect to the longitudinal axis 307. As shown, this “conicalinterference” interface 324 is a “conical interference interface,” whichcan have a linear dimension of about 0.001 to 0.003 inches. In someembodiments, the conical interference interface 324 can be pressed andcrimped, e.g., to about 2000 lbF. The inner body portion 302 alsoincludes an exterior surface 322. The exterior surface 322 can include aconical datum feature that is aligned to the through bore. The outerbody portion 304 can have an “axial stop” 306. The conical interferenceinterface 324 and/or the axial stop 306 can help align the inner bodyportion 302 to the outer body portion 304 and the longitudinal axis 307.

FIG. 4 is a cross-sectional diagram of another improved double nozzle400 for a laser cutting system, according to an illustrative embodimentof the invention. The double nozzle 400 includes an inner body portion402 having an inner nozzle bore 412 and an outer body portion 404 havingan outer nozzle bore 414, which are oriented along a longitudinal axis407 of the laser beam. The double nozzle 400 has a similar configurationto the double nozzle 300 shown and described above in FIG. 3 withrespect to the “conical seating” arrangement, although the FIG. 4configuration does not employ the reduced number of interface surfacesshown in FIG. 2. In the FIG. 4 configuration, the inner body portion 402is conically seated within the outer body portion 404. The conicalseating itself improves alignment of inner nozzle bore 412 and outernozzle bore 414 with respect to the longitudinal axis 407 (and hence thelaser beam), independent of the benefits of the redesign shown in FIG.2.

Generally, coaxiality of the inner body portion and the outer bodyportion can be further improved by avoiding slip fits and press fits infavor of a clearance fit, with inner and outer body portions adjusted toa coaxial position via precise tooling and subsequently attached to eachother (e.g., via screws, tabs, welds, glue bonds, solder joints oranother method that results in the two parts being fixed in a highlypositioned coaxial arrangement). In some embodiments, the inner andouter body portions can be made to have a low impedance, highconductivity bond (e.g., to allow for high frequency AC capacitiveheight sensing signals to pass between the inner body portion and theouter body portion). Such a configuration can be achieved through directcontact of fasteners, conductive elements within expox mix, soft solder,silver braze, or welding (e.g., laser welding, friction welding, orebeam welding). Alternatively or in conjunction with the screwed and/ortapered surfaces for alignment discussed herein, nozzles can be formedpre-aligned and fixtured, and/or glued or otherwise welded, bonded,fastened and joined for industrial cutting applications and solutions.

In some embodiments, uniformity of the double nozzle flow is importantto the consistency of the cut process. Currently, most double nozzlesare characterized by an inner nozzle with a tri-lobe feature and threeslots to meter and distribute the flow about the central process gasbore. However, these three slots can create a non-uniform flow withinthe double nozzle. In contrast, in some embodiments, the invention usesmore than three slots. For example, FIG. 4A shows a double nozzle 450having twelve slots 455A-L, and FIG. 4B shows a double nozzle 460 havingsix slots 465A-465F. The configurations of the nozzles 450, 460 canimprove alignment between nozzles 450 and 460 as well as enhance theprocess consistency and cut quality over traditional three-slot orthree-bore configurations. In some embodiments, the distinct flowpassages including the “slots” shown in FIGS. 4A-4B can take a varietyof other forms, e.g., can be holes, grooves, channels, or other featuresconfigured to form distinct co-axial fluid flow paths through the doublenozzle and/or to improve fluid flow and decrease non-uniformity of fluidflow (e.g., from the perspective of the laser beam). In the industry,the conventional wisdom has been to form flats or drill holes, ratherthan to use a form of “scalloped” slots or other features, because ofthe complexity that these features introduce (e.g., in construction ofthe parts), and in this respect the invention moves away from thisconventional teaching. With the “slots” or corresponding features boredout of at least one of the inner or outer nozzle portions, correspondingfeatures are naturally generated in the remaining terrain of therespective nozzle portion, e.g., ribs, struts, walls, or partitions(such as features 459A-L or features 466A-F).

As shown in FIG. 4A, compared to conventional three slotted doublenozzles there are more points or areas of contact in the interfaceregion between the exterior surface of the inner nozzle 460 and theinterior surface of the outer nozzle 461. In some embodiments, thisincreased number of contact areas (e.g., points of contact and/or pointsof alignment influence) results in an improved alignment between innernozzle 460 and outer nozzle 461. For example, if the inner nozzle 460includes twelve (or six, or another number greater than three)corresponding ribs for making contact, the effect of any one rib beingout of alignment can be negligible, as there are still more thansufficient ribs to ensure proper alignment. However, using a designhaving only three ribs, if one rib is out of alignment, there are onlytwo others to compensate, which can mean a larger total effect onalignment or misalignment for the whole configuration as each rib canhave a greater impact, effect or influence on alignment under thesecircumstances. In addition, in some embodiments the total amount ofcontact surface area between the inner nozzle 460 and the outer nozzle461 is reduced. Some past designs have included significant surface areacontact between the inner and outer nozzles, which can providehigher-than-needed opportunities for misalignment (e.g., due to surfaceimperfections on the parts). In addition, it is not always obvious orpractical to notice and/or correct such deficiencies in the field. Incontrast to the conventional teachings, FIG. 4B shows a reduced contactsurface area between the ribs 466A-466F of the inner nozzle 460 and theouter nozzle 461, reducing the opportunities for misalignment. Usingsuch configurations, an improvement of about 50% improvement inalignment has been observed: whereas prior art embodiments have seendiscrepancies in alignment of about 0.003 inches between an inner nozzleand an outer nozzle, configurations in accordance with the principles ofFIG. 4B can achieve discrepancies of about half that amount, e.g., about0.0015 inches.

Further, as shown in FIG. 4B, each of the features of the currentinvention has a comparatively smaller contact area and circumferentialwidth than the comparable counterpart ribs on the conventional threeslot design. This reduction in circumferential width results in a moreuniform and consistent gas flow between the inner nozzle 460 and outernozzle 461 as these interfaces between the inner nozzle 460 and theouter nozzle 461 have a reduced effect on gas flow interrupted by theirpresence and as such limit the size of downstream flow dead spots.

FIG. 5A shows a three-dimensional measured flow mapping of a standardthree-slot design for a double nozzle, while FIG. 5B shows athree-dimensional measured flow mapping of a six-groove design for adouble nozzle, according to an illustrative embodiment of the invention.The FIG. 5B diagram shows improved (e.g., more even or radiallysymmetric) distribution, including with fewer interruptions incomparison to the FIG. 5A. In particular, FIG. 5A shows non-uniformityof the outer flow, and the bumps (e.g., bumps 501 and 502) and dips(e.g., dip 503), caused by corresponding slots, can be easilyvisualized. The bumps shown in FIG. 5A are diametrically opposed to theslot location, and the dips fall in between the bumps, indicating thatthe slot flow “shoots” across and under the inner nozzle to exit thenozzle bore at a diametrically opposite location. In contrast, FIG. 5Bshows that in the six-groove design, the outer pressure shelf is moreuniform (e.g., less impacted by the more numerous but comparativelysmaller features). Thus, the flow characteristics within the doublenozzle can be dramatically impacted by the shape and/or size of thefeatures (e.g., slots, holes, or other features) defining the fluidpassageways.

FIG. 6 shows a perspective view of an inner body portion 600 of a doublenozzle, according to an illustrative embodiment of the invention. Asabove, the inner body portion 600 defines six features (e.g., slots601A-601F, which when mated with the outer body portion form six flowpassages about the central bore) in between six corresponding “ribs” orfeatures 602A-602F. In some embodiments, the features 601A-601F have a“scalloped” shape, or another shape with a defined curvature. In someembodiments, the features 602A-602F further include step features (e.g.,603A and 603F as depicted, with corresponding features for the remainingribs not visible in this view) that assist with seating and alignment ofthe inner body portion 600 relative to the outer nozzle (not shown)during assembly. In some embodiments, the step features 603A-603F helpto reduce the area over which an interference fit is needed, which canhave benefits for assembly, such as reduced likelihood of pinching,rocking, or misalignment. In some embodiments, the slots can be formedin the outer nozzle, in addition to or alternatively to being formed inthe inner body portion 600. In some embodiments step features 603A-603Fmay be located in the rearmost portion of inner body portion 600 (e.g.,occupying about less than the back 20% of the inner body portion, in oneembodiment occupying about less than the back 10% of the inner bodyportion). Features 601A-601F are raised radially outward slightlyrelative to the forward portions of features 602A-602F. Features602A-602F are sized to contact an interior surface of outer nozzle 461during assembly, the six features roughly aligning inner body portion600 with outer nozzle 461 during the initial part of assembly. Then onceinner body portion 600 is substantially inserted within outer nozzle 461(e.g., greater than about 50% inserted or in some cases greater thanabout 80% inserted longitudinally) step features 603A-603F begin tocontact an interior surface of outer nozzle 461 in an interference fitstyle fashion, further driving alignment between inner body portion 600and outer nozzle 461 and securing inner body portion 600 within outernozzle 461.

FIG. 7 shows a cross-sectional view from the side of the nozzle of onepossible step feature 702 of a double nozzle, according to anillustrative embodiment of the invention. In this view, an outer nozzle704 and an inner nozzle 706 are shown interfacing at or near the stepfeature 702. The outer nozzle 704 includes an interior surface 708(depicted without diagonal shading). In this embodiment, the stepfeature 702 can be formed in the outer nozzle 704 and perform the sameor substantially the same function as described above.

While the invention has been particularly shown and described withreference to specific preferred embodiments, it should be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit and scope of theinvention as defined by the following claims.

What is claimed is:
 1. A double nozzle for a laser processing head, thedouble nozzle comprising: an inner body portion having (i) an interiorsurface defining a first bore, and (ii) an exterior surface, the borealigned with a central longitudinal axis of the body; and an outer bodyportion having an interior surface defining a second bore that issubstantially aligned to the longitudinal axis, the outer body portionmatingly engaged with a region of the exterior surface of the inner bodyportion, wherein the region between the exterior surface of the innerbody portion and the interior surface of the outer body portion definesat least six coaxial fluid flow paths through an interior annular flowvolume of the double nozzle, each fluid flow path defined at least inpart by a corresponding feature formed in at least one of the inner bodyportion or the outer body portion.
 2. The double nozzle of claim 1wherein the region includes an interface between the exterior surface ofthe inner body portion and the interior surface of the outer bodyportion.
 3. The double nozzle of claim 1 wherein the coaxial fluid flowpaths are shaped to increase fluid flow and uniformity of fluid flowthrough the double nozzle.
 4. The double nozzle of claim 1 wherein eachof the fluid flow paths is defined at least partially by a correspondingfeature in the exterior surface of the inner body portion.
 5. The doublenozzle of claim 1 wherein each of the fluid flow paths is defined atleast partially by a corresponding feature in the interior surface ofthe outer body portion.
 6. The double nozzle of claim 1 wherein each ofthe fluid flow paths includes a scalloped or curved surface.
 7. Thedouble nozzle of claim 2 wherein the interface between the exteriorsurface of the inner body portion and the interior surface of the outerbody portion is at least partially defined by one or more step features.8. The double nozzle of claim 1 wherein each of the features isconfigured to assist with seating and alignment of the inner bodyportion relative to the outer body portion during assembly of the doublenozzle.
 9. The double nozzle of claim 1 wherein the substantialalignment is less than about 0.002 inches.
 10. The double nozzle ofclaim 1 further including a second exterior circumferential surface ofthe inner body portion that is tapered at an angle of 4.5 to 5.5 degreeswith respect to the longitudinal axis.